P-51 Mustang

The North American P-51 Mustang was a successful long range fighter aircraft which entered service in the middle years of World War II. The definitive version of the single-seat fighter was powered by a single two-stage supercharged V-12 Merlin engine and armed with six .50 caliber (12.7 mm) M2 machine guns.

First versions

The result of the MAP order was the NA-73X project from March 1940. The design was in keeping with the best conventional practice of the era, but included two new features. One was a new NACA-designed laminar flow wing, which was larger than others on similar aircraft while still having the same drag. This left plenty of room for landing gear, guns, ammunition and fuel, all completely inside the wing and well streamlined. Another was the use of a new radiator design from Curtiss, that used the heated air exiting the radiator as a form of jet thrust.

Related Topics:
NACA - Laminar flow - Landing gear

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The USAAC could block any sales they considered interesting, and this appeared to be the case for the NA-73. An arrangement was eventually reached where the RAF would get its planes, in exchange for NA providing two more cost-free to the USAAC.

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The plane made its maiden flight on 26 October 1940, 178 days after the order had been placed - an incredibly short period. In general, the plane handled well and the internal arrangement allowed for a massive fuel load. It was armed with four 0.5 in (12.7 mm) machine guns and another four 0.3 in (7.62 mm) guns - a rather light armament load for the era: the contemporary Focke-Wulf Fw 190 prototype was able to carry four 20 mm cannon and two 7.92 mm machine guns.

Related Topics:
26 October - 1940 - Cannon

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It was quickly evident that performance, although good near sea level, was not up to European standards at higher altitudes. This was due largely to the mechanically supercharged Allison V-1710 engine. The finer points of supercharging were very much a British specialty: United States engineers had concentrated mainly on the turbocharger instead and the Allison suffered in consequence.

Related Topics:
Supercharged - Allison V-1710 - Turbocharger

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About 20 of the Mustang I were delivered to the RAF and made their combat debut on 10 May 1942. With their long range and excellent low-level performance, they were judged useful for ground-attack duties over the English Channel, but too slow at altitude to be used as fighters.

Related Topics:
10 May - 1942 - English Channel

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The Mustang Mk.IA removed the 0.3 in (7.62 mm) guns in an effort to improve performance. At the same time the USAAC was becoming more interested in ground attack planes and had a new version ordered as the A-36 Apache which included two more 0.5 in (12.7 mm) guns, dive brakes, and could carry two 500 pound (230 kg) bombs. Neither of these versions were particularly effective.

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